Detection of rectal cancer and response to concurrent chemoradiotherapy by proton magnetic resonance spectroscopy

IntroductionTo diagnose rectal cancer and monitor treatment response after preoperative concurrent chemoradiotherapy (CCRT) in rectal cancer patients using proton-1 magnetic resonance spectroscopy (1H-MRS).Materials and MethodsWe enrolled 134 rectal cancer patients before treatment, of whom 34 underwent preoperative CCRT and follow-up MR spectroscopy before surgery. 1H-MRS was performed using a six-channel phased-array coil at 3.0 T. We evaluated the presence of a choline peak at 3.2 ppm, and lipid peaks at 0.9 and 1.3 ppm, and glutamine and glutamate peaks at 2.1-2.3 and 2.7 ppm seen at two TEs (40 and 135 ms). We divided MR spectra patterns into two groups (A and B).ResultsA choline peak at 3.2 ppm seen in both TEs was characteristic for rectal cancer before treatment. Of 103 patients, 55 (53%) showed an elevated choline peak before treatment (type A). Type A spectra were seen in 68% of patients (23/34) before preoperative CCRT. After CCRT, the choline peak disappeared, resulting in only the lipid peak at 1.3 ppm (type B) in 97% of patients (33/34).DiscussionWe optimized a localized in vivo1H-MRS method for detection of rectal adenocarcinoma and monitoring treatment response after preoperative CCRT. The method appears to be a promising and feasible noninvasive modality.